The present invention relates, in general, to electron emission devices, and more particularly, to a novel extraction grid for an electron source.
Field Emission Devices (FEDs) are well known in the art and are commonly employed for a broad range of applications including image display devices. An example of a FED is described in U.S. Pat. No. 5,142,184 issued to Robert C. Kane on Aug. 25, 1992. FEDs typically have a plurality of closely spaced electron emission tips or emitters that are utilized to illuminate a pixel on a phosphor screen. An emission gate or extraction grid typically is positioned between the emitters and the screen, and is utilized to stimulate electron emission from the emitters. The extraction grid has a hole over each emitter in order to allow electrons to travel from the emitter to the screen. As the electrons travel the distance from the extraction grid to the screen, the electrons diverge thereby resulting in an image having an area that is larger than the area of the extraction grid. This divergence makes it difficult to focus a pixel into a sharp image.
Accordingly, it is desirable to have an electron source extraction grid that reduces divergence of the electron beam that passes through the extraction grid of the electron source.